Such open-end spinning devices are, for example, known from German Patent Publication DE 43 34 485 A1 which discloses a typical open-end spinning unit with a yarn conduit plate and a conduit plate adapter. The yarn conduit plate closes the front side of the rotor housing and is part of a pivotable cover forming a part of a spinning box housing assembly which covers the entire front side of the spinning box and additionally carries an intake roller and an opening device for the sliver as well as a soil separation chamber. The yarn conduit plate can be an integral component or a detachable part of the pivotable cover. The conduit plate adapter is removeably positioned in the yarn conduit plate. The conduit plate adapter contains a part of a yarn guide conduit, a yarn draw-off jet and a connection to a yarn draw-off tube.
In order to assure a precise yarn infeed and an optimal yarn draw-off, conduit plate adapters are coordinated with a certain rotor shape and size. Upon a yarn batch change, the rotor must also be replaced. Thus, the conduit plate adapter is replaced by a conduit plate adapter which is compatible with the new rotor.
Various fastening devices have been suggested to simplify the replacement of the conduit plate adapter. For example, German Patent Publication DE 43 34 485 A1 teaches fastening the conduit plate adapter with screws to the conduit plate. However, a disadvantage of this type of device is that it requires the use of tools. A fastening device for a conduit plate adapter which can be replaced without tools is described in German Patent Application DE 195 24 837 A1. The conduit plate adapter comprises a conical bearing body which is inserted into a corresponding conical receptacle of the onduit plate. In this device, a bar spring engages on one side into a tangential groove in the conical bearing body to fasten the conduit plate adapter. The conduit plate adapter is released by bending the spring back. While the conduit plate adapter may be fastened and released without tools, one disadvantage of this design is that the off-center introduction of force by the spring at one side of this device can cause a tilting of the conical bearing body of the conduit plate adapter and may cause leaks which result in the undesirable inflow of infiltrated air into the spinning chamber.